An electronic intensive engine control of vehicle by using a microprocessor is described for example in Tokkai Sho 55-151133 published by the Japanese Patent Office in 1980.
When the ignition switch is turned to the START position, a starter cranks the crankshaft. Simultaneously, an electronic control unit (ECU) computes a starting infection pulse width, and a signal representative of this pulse width is sent to the fuel injector. The fuel injector injects an amount of fuel corresponding to this signal into an intake pipe, and the engine starts.
After start-up, the ECU computes a suitable fuel infection pulse width according to the change of engine running conditions, and controls the fuel supply to the engine. This permits fine control of the fuel supply, and the unit also controlling the ignition timing depending on the running conditions.
However, if the ECU breaks down while the vehicle is running, fuel injection and ignition are no longer possible, and the vehicle stops wherever it happens to be. It is therefore expedient to provide a backup mechanism that, independently of the ECU, can inject a constant amount of fuel and ignite it at a constant crankshaft rotation position, so that the vehicle can at least reach a repair station. Such a backup mechanism may for example be provided by a hybrid IC and gate array.
If such a backup mechanism is provided, the backup mechanism operates so that the vehicle still runs even if the ECU is damaged, or the signal line from the ECU to the hybrid IC is cut. Hence, even if the ECU has an anti-theft mechanism so that the vehicle will not start even if, for example, the contact of the ignition switch is connected, the engine can still be made to start by breaking the ECU. In other words, the back-up mechanism may render the anti-theft mechanism useless.